When to plant marigold in Manchester, New Hampshire

April 30 – May 14

Transplant outdoors · typical Manchester year

Climate basis: NOAA station Massabesic Lake, NH (USC00275211), 4 mi (6 km) from downtown Manchester (ZCTA 03101 centroid), elevation 253 ft, on the 1991–2020 climate normals. Transplant marigold outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (April 30). One year in ten still freezes after May 14.

Last spring freezeApril 301-in-10 after May 14

First fall freezeOctober 111-in-10 before Sep 30

Frost-free season≈ 164 daysmedian at 32°F

Hard freeze, 28°Apr 17 – Oct 24kills even hardy greens

USDA zone6a-10 to -5°F winter low — not frost timing

The Manchester year

Start seeds indoorsMar 5 – Mar 19

Transplant outdoorsApr 30 – May 14

Direct-sow outdoorsApr 30 – May 14

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 14

Marigold in Manchester · freeze context from Massabesic Lake, NH, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Mar 5 – Mar 19

Sources disagree on indoor timing - UW-Madison says about 8 weeks and UMN about 10 weeks before the after-frost outdoor planting date - and the later, more conservative 8-week start wins, giving 56 to 42 days before last frost. Anchored to the median last spring freeze (Apr 30). University of Wisconsin-Madison Division of Extension · University of Minnesota Extension · Iowa State University Extension and Outreach

Transplant outdoors

Apr 30 – May 14

UMN, UW-Madison and Iowa State all agree that marigold plants go out once danger of frost has passed, so the set-out window opens at the last-frost date and runs two weeks. Anchored to the median last spring freeze (Apr 30). Iowa State University Extension and Outreach

Direct-sow outdoors

Apr 30 – May 14

Iowa State University Extension is the only one of the three sources to anchor direct seeding to frost rather than soil temperature ('Sow marigold seeds outdoors when the danger of frost is past'), giving a two-week window from the last-frost date; UW-Madison's and UMN's 65F soil-temperature rules cannot be frost-anchored and were not encoded. Anchored to the median last spring freeze (Apr 30). University of Wisconsin-Madison Division of Extension · University of Minnesota Extension · Iowa State University Extension and Outreach

Variety assumption: Covers Tagetes marigolds (French, African/American and signet types) only; pot marigold / calendula (Calendula officinalis) is a different plant and is not encoded here.

These windows describe typical years (1991–2020 climate normals), not this year's forecast. Freezes happen outside them — especially in frost pockets, valleys, and urban edges. Watch the forecast before committing tender plants.

This week, not a typical year:

Crop rule sources (3)

University of Wisconsin-Madison Division of Extension: Marigolds - Wisconsin Horticulture (accessed 2026-07-25)
"Marigolds can be direct seeded into garden soil when soil temperatures are >65°F or seeds can be started indoors ~8 weeks prior to transplanting outdoors after the threat of frost has passed."
University of Minnesota Extension: Marigolds (accessed 2026-07-25)
"Marigold seeds can be started indoors about 10 weeks prior to the anticipated outdoor planting date."
Iowa State University Extension and Outreach: When can I plant marigolds outdoors? | Yard and Garden (accessed 2026-07-25)
"Plant marigold seedlings outdoors after the danger of frost is past."

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